Does anyone know if this could of caused any other issues?

Put extra strain on gearbox or any other parts?

Thanks

My concern is gearbox has done 116k miles. Could the diff issue have put extra strain on the gearbox?

good advise already given here...
i had a similar issue 3 years ago.

start with home insurance legal cover for advice
keep track of all conversations and communication with garage and warranty company..
SOGA is in your favour.(though court cases are not a done deal)
can you get the repair done and then bill the garage? if they don't pay....claims court + expenses
def to pursue it...its a pain for all concern though..

Good news. Booked into Guy Salmon in couple of weeks for new front diff and he's paying!

Glad it's finally going to be sorted.